The present invention relates to a data transfer apparatus and a data transfer method, and specifically to a way of transferring image data.
Generally, an amount of image data is so large that the capacity of an internal memory built in a system is not enough. Thus, a high-capacity external memory is often used as a shared memory to store such data.
An update of the image data and other application processes are then performed on the shared memory. The shared memory is also accessed by other peripheral modules such as a processor, a camera, and the like.
When transferring the image data to a display or the like, generally a part of the image data is buffered in an image buffer memory because a response time from a read request to a read data output is long in the external memory.
A display transmitter then reads the image data buffered in the image buffer memory and outputs the image data to the display.
On the other hand, when the image buffer memory accesses the shared memory and competes with another module for the access, the data access by the image buffer memory may delay, buffering of the image buffer memory may not be done in time, and an underflow may occur to the image buffer memory. This delay of the buffering in the image buffer memory may disturb an image on the display.
Japanese Unexamined Patent Application Publication No. HEI6(1994)-175646 proposes a method of devising a buffering technique.